Introduction: Plasma vascular endothelial growth factor (VEGF) levels are increased after surgery and may stimulate tumor growth after cancer resection. Angiopoietin 1 (Ang 1) and Ang 2 are proteins that impact VEGF-related angiogenesis (VRA). Ang 1 stabilizes mature vessels and inhibits VRA, whereas Ang 2 destabilizes vessels and promotes VRA. The ratio of Ang 1 to Ang 2 reflects the net effect; a low ratio promotes VRA. This study's purpose was to determine the impact of open and minimally invasive (MIS) colorectal resection (CR) for benign indications on plasma Ang 1 and 2 levels. Methods: A total of 30 patients operated by MIS and 26 operated by open procedure were studied. Plasma was obtained preoperatively (PO) and on postoperative days (POD) 1 and 3. Plasma Ang 1 and Ang 2 levels were assessed via enzyme-linked immunosorbent assay (ELISA) in duplicate. Data were compared using Wilcoxon's matched-pair test and the Mann-Whitney U-test (significance p < 0.05). Results: Indications, types of resection, and morbidity for the groups were similar. The mean MIS incision length was 4.7 ± 1.6 cm while it was 16.8 ± 7.1 cm for the open group (p = 0.0001). For both groups Ang 2 levels were significantly higher and the Ang 1 to Ang 2 ratio was significantly lower on POD 1 and 3 compared with preoperative results. Ang 1 levels were significantly decreased on POD 1 and 3 in the MIS group but only on POD 1 in the open group. For unclear reasons, preoperative Ang 1 levels and Ang 1 to Ang 2 ratios were significantly different between the groups, which precludes comparison of the postoperative results between groups. Conclusion: CR for benign pathology results in higher Ang 2 levels, lower Ang 1 levels, and lower Ang 1 to Ang 2 ratios early after surgery. These alterations are proangiogenic. These results, plus the already noted VEGF increases, suggest that surgery results in proangiogenic plasma protein changes that may stimulate tumor growth early after surgery. The duration of the Ang 1 and 2 changes needs to be determined.
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